Crane safety device



B. F. FY'ITCH CRANE SAFETY DEVICE Filed July ll, 192,5 2 Sheets-Sheet lgvwwntoz GHQ: 11 M14 Jan. 31, 1928.

B. F. FITCH CRANE SAFETY DEVICE 2 Sheets-Sheet 2 Filed July 11, 1925Patented Jan. 31, 1928.

BENJAMIN IF. FITCH, OF GREENWICI-I, CONNECTICUT.

CRANE SAFETY DEVICE.

Application filed July 11,1925. Serial No. 42,891.

This invention relates to a mechanism which is adapted for use 1nconnection with the raising of a load by means of a crane.

In the operation of a crane embodying a screw and nut couple, one memberof which is rotated, while the other member is moved along the crane andis attached to the load, there is considerable strain placed upon thethreaded portions of the coacting member especially when a heavy load isbeing raised or lowered. Moreover, if any wear should occur in suchthreaded portion it is difiicult to determine the extent of such wearwithout dismantling a large part of the crane structure.

One of the objects of the present invention is the provision of a safetyappliance which may be used in connection with the operation of a craneembodying a screw and nut couple as part of the hoisting mechanism. Moreparticularly, my invention contemplates the provision of an emergencynut which normally functions without bearing any of the load stresses,but which is adapted to counteract such stresses and thereby to preventdamage in the event of failure of the threaded portion between the screwand nut couple.

I have illustrated my invention in connection with an overhead travelingcrane wherein Fig. 1 is a plan view of such crane; Fig. 2 is a plan viewon an enlarged scale showing the emergency nut feature embodying myinvention; and Fig. 3 is a section taken on the plane indicated by theline 3-3 in Fig. 2. i

The crane which I have illustrated in con nection with my invention isillustrated as being supported by Wheels 10 which travel on an overheadtrack 11. The wheels are journalled within a frame which may compriselongitudinal members 12 and transverse members 13 which are arranged inthe form of a rectangle. The frame work may comprise channel beams whichare held to:

get-her in any convenient manner.

The hoisting mechanism shown comprises cables 14, 15, 16 and 17 whichextend over sheaves 18, 19, 20 and 21 respectively. The

Ysheaves are arranged adjacent the corners of a rectangle whereby thevertical reaches of the cables may-engage a removable truck bodyadjacent the four corners of 2. rectangle. To move the sheavessimultaneously I have shown a screw and nut couple which is disposedadjacent the mid portion of the frame. The load carrying nut 7, asshown, is attached to the cables and is arranged to be guided whilemoving longitudinally of the frame by guides 22 and 23. Such movement iseffect-ed whenever the screw or threaded shaft 24- is rotated.

An important advantage of my invention is the fact that a simpleexpedient is provided for insuring safe operation of the hoistingapparatus against failure of thethreads on the nut where a screw and nutcouple is employed in connection with such apparatus. A furtheradvantage is the fact that normally the emergency nut is out of contactwith the load bearing nut, wherefore, the emergency nut normally assumesno load stresses during the normal operation of the load bearing nut.

In the preferred form, the safety appli ance embodying my inventioncomprises an emergency nut indicated at 8 which may be threaded onto theshaft 24: so as normally to be. out of contact with the nut 7 but to beoperatively connected therewith, if the nut 7 should fail. As shown theconnection is made by pins 9 which are rigid with the nut 8 but areloosely mounted in sockets 4: in the other nut. The nut 7 is ordinarilymade of bronze and is arranged to carry all of the load stress while thenut 8 is preferably made of steel and is normally inactive but may carrythe load as an emergency.

In the event of failure of the nut 7 dueto wear on the threads, the nut7 will be forced against. the nut 8 whereupon the load stress will thenbe placed upon the emergency nut. The pins prevent one nut from turningwith reference to the other nut while the guides prevent the loadbearing nut from turning whenever the shaft is rotated. In this way, Iprovide an emergency feature which would be sufficiently strong tosupport the load for a limited time.

I claim:

In a hoisting mechanism, the combination with a frame, of a rotatablescrew shaft mounted thereon, a main nut in threaded engagement with theshaft, a plurality of eye-bolts extending through the main nut onopposite sides of the shaft and adapted to be attached to loadsupporting cables. said main nut having a plurality of sockets thereinopening in a direction toward the cables, an emergency nut spaced fromthe main nut andin threaded engagement with the shaft and having pinscarried thereby and projecting into said sockets, the depth main nut.

In testimony whereof, I hereunto nfiix my signature.

BENJAMIN F. FITCH.

